Aging is associated with a decline in motor ability which has been typically described in terms of muscle weakness leading to postural instability and locomotor difficulties. In contrast, our understanding of how age-related changes in somatosensory feedback affects motor function is remarkably poor. This is particularly true for the upper limbs despite the importance of arm and hand use in many activities of daily activity and the maintenance of functional independence. In particular, proprioceptive feedback arising from muscle stretch, cutaneous, and force receptors is critical not only in providing an awareness of body position, but in the generation, learning, and on-going control of goal-directed limb movements. Given the paucity of data in this area, the aims of this study are: 1) to provide much needed baseline information regarding upper limb proprioceptive acuity in older individuals and to determine whether changes in motor function are related to changes in proprioceptive function, 2) to determine whether physical activity impacts proprioceptive acuity in older individuals, and 3) to determine if proprioceptive acuity differs between the dominant and non-dominant hands. Young (20-30 yrs) and two groups of elderly subjects 70 yrs and older (sedentary vs active) will be examined. Wrist position and hand grasp force matching paradigms will be used in which movements/forces are produced based solely on limb position or force reference information. Matching tasks will vary in complexity by requiring subjects to match the movement or force with the same or opposite limb. Instrumented levers and force transducers will be used to measure wrist movement and grasp force, respectively. In the limb matching conditions, a servomotor will be used to passively displace the joint at a constant slow velocity. This study will form the foundation for a longer-term research program examining sensorimotor function in the elderly, including disease conditions which impact mobility, and with a focus on maintenance and/or improvement in upper limb function through, for example, training-based interventions.